The invention relates to new and useful improvements in a front system for mounting a printed circuit board onto a mounting rack. More particularly, the invention relates to a front system provided with a push-button element used for switching the circuit board between active and passive states.
EP 0 304 772 B1 discloses a front plug system for a flat structural component (printed circuit board) having an end contact device. In this case, a front plug connector can be plugged onto a front element which is located at the end of a printed circuit board assembly. This is carried out by means of a pivot movement, in that the front plug connector can be attached into a pivot bearing at one end of the front element. Located at the other end of the front element and front plug connector is an end contact device which does not engage until after the front plug connector is attached completely to the front element. The engagement is achieved through operation of a closure device, which is preferably provided by a screw that is likewise inserted into the other end of the front plug connector, so that the operating contacts of the end contact device do not engage until the screw has been screwed completely into an oppositely located thread in the front element, and the front element has thereby been attached completely. In this way, it is possible to ensure that the electrical signals which are passed via the front element and the front plug connector are not released until all the contacts between the front element and the front plug connector have been closed, this release of the electrical signals taking place simultaneously. Conversely, it ensures that the front plug connector is restricted before one of the contacts is interrupted when the front plug connector is pivoted away.
Printed circuit board assemblies can be levered into and out of the plug-in slot in a mounting rack by means of insertion and withdrawal aids such as those known, e.g., from EP 0 194 515 B1. However, even in the case of such printed circuit board assemblies that can be levered in and out, it is sometimes necessary to bring about organized release and/or interruption of the entire signal exchange, which proceeds via their rear plug connectors to a mounting rack motherboard and a data bus located there. Thus, e.g., at the start of levering out a printed circuit board assembly, it is desirable to bring about complete interruption of the signal exchange to and from the printed circuit board assembly without having to disconnect the contact between the plug connector and the motherboard, even though other contacts are not yet disconnected.
In order to solve this problem, the document Honeywell Outline, Sensors and Automation, Year 9, Issue 1, pages 10, 12 proposes, in the article "Leiterplatten-ausbau ohne Systemunterbrechung mit Honeywell Schaltern und Sensoren" Printed circuit board removal without system interruption using Honeywell switches and sensors! that, for example, a switch be fitted to the edge of the printed circuit board, either on its top or bottom, and be connected to the main power supply, e.g. via appropriate conductor tracks. An interlocking mechanism, which fixes the printed circuit board in its position in the mounting rack, acts on the switch. In the interlocked state, a bolt of the interlocking mechanism rests on that edge of the printed circuit board to which the switch is fitted and causes the switch to operate, and thus causes electrical activation of the printed circuit board. If, in contrast, the bolt is pivoted away from the edge, then the switch is interrupted and the printed circuit board is switched to be electrically inactive. An infrared component can also be used instead of the switch.